1. Field of the Invention
This invention relates in general to data communication between processors and storage devices, and more particularly to a method and apparatus providing simultaneous connection of a plurality of controllers to a plurality of serial storage devices and serial storage device sets.
2. Description of Related Art
The parallel ATA interconnect has been the dominant internal storage interconnect for desktop and mobile computers since originally introduced in the 1980s. Parallel ATA has been used to connect storage devices such as hard drives, DVD and CD drives, and others to the motherboard. Parallel ATA's relative simplicity, high performance, and low cost has made possible the cost/performance ratio that is essential in the mainstream desktop and portable PC market.
However, parallel ATA has a number of limitations that are exhausting its ability to continue increasing performance. For example, in the near future, integrated circuits manufactured on the leading manufacturing processes will not be able to efficiently support 5-volt signaling voltages. Further, parallel ATA, with its 26 signals, requires a 40-pin connector and uses an unwieldy 80-pin ribbon cable to route inside the chassis. This high pin count is problematic for chip design and makes it difficult to route traces on a motherboard. The wide ribbon cable impedes airflow in the chassis, making thermal design more difficult. These issues become especially acute in notebooks and small form factor desktops, servers, and networked storage. Also, parallel ATA disk drives are limited by their signal and power connectors to cable-attached applications and do not facilitate hot-plugging.
Serial advanced technology attachment (S-ATA) is intended to replace today's parallel ATA. Serial ATA is designed to address many of the limitations of parallel ATA, while maintaining 100% software compatibility. This will significantly ease the transition to Serial ATA, as no changes in today's drivers and operating systems should be required. Serial ATA enables the industry to move to thinner cabling, lower pin counts, lower power requirements, higher performance and hot plug capability.
Serial ATA (S-ATA) is intended to become the dominant interface for the desktop disk drive market. With its cost advantages and the ability to hot plug devices, S-ATA also provides great value for servers and redundant array of inexpensive disks (RAID) applications.
However, a couple of significant problems with S-ATA have been identified. The problems arise mainly from S-ATA being a point-to-point technology. Being a point to point technology means that only one controller can attach to a given drive at a time. Additionally, S-ATA requires a single interface port for each drive. Therefore, if the controller should fail, the disk drive becomes inaccessible.
Building large systems that use S-ATA and have access to a plurality of disk drives has been hampered because of these inadequacies. It would be desirable to create a vast data networking system that uses channel based switch fabric architecture having enhanced scalability and performance. Another goal is to overcome the disadvantages of S-ATA and produce a more reliable high speed I/O data transfer environment having excellent throughput and a high level of functionality.
It can be seen that there is a need for a data communication system with vastly increased scalability and enhanced reliability that provides a plurality of controllers simultaneous and independent access to a plurality of serial storage devices.
It can also be seen that there is a need for a device that provides inter-connective access of a plurality of controllers to a plurality of serial storage devices that can be used as the interconnect mechanism to increase the number of S-ATA ports, as well as provide a path from a plurality controllers to the same set of serial storage devices.